1. Field of the Invention
The present invention relates generally to a control system such as used in connection with automotive engines and/or transmissions and, more specifically, to an arrangement for determining the opening degree of an engine throttle valve or the like type of control member.
2. Description of the Prior Art
Electronic control circuits for automatic automotive transmissions require the input of a signal indicative of the opening degree (position) of the engine throttle valve. In order to achieve this input, a throttle position sensor is operatively connected with the throttle valve and arranged to output a signal indicative of the position to an electronic control unit. An example of such an arrangement is shown in FIG. 5. This arrangement has been disclosed in Nissan Skyline Service Manual E-FR32 type, published by Nissan Motor Co. Ltd in March of 1989.
As shown in FIG. 5, this particular type of arrangement includes a sensor 50 which is arranged to output an analog signal. This signal is supplied to an engine control circuit 52 which includes an A/D converter 54 which converts the inputted signal to a digital form. The digital signal is supplied to a central processing unit (CPU) 56. The engine control circuit 52 further includes a voltage follower 58 which is connected to an A/D converter 62 forming part of a transmission control circuit 60. This A/D converter 62 is operatively connected with a central processing unit 64 which forms part of the control circuit 60 in a manner which permits the digital signal to be supplied thereto.
In this manner, both the engine and transmission control circuits are supplied with a signal indicative of the engine throttle valve opening degree.
However, this arrangement has suffered from the drawback that three connection lines between the two control circuits 52, 60 are necessary. Viz., in addition to the analog signal indicative of the throttle valve opening, a source of reference voltage and an earth connection are additionally necessary.
Further, in the event that the output of the throttle valve position sensor is subject to adjustment, both of the engine and transmission control circuits must also be adjusted. That is to say, when the throttle valve position sensor is fitted to the engine for example, due to unit deviation, it is necessary to adjust the system so that the output of the sensor accurately reflects the position of the throttle valve. For example, when an adjustment of the nature disclosed in JP-A-63-180755 is carried out, as both of the transmission and engine control circuits receive an analog output from the sensor 50, it is essential that both of the circuits be adjusted so as to both reflect the same positions. If this is not done, it is possible that the engine and transmission control circuits will take the same signal as indicating different throttle positions and give rise to the possibility that the proper coordination between engine torque control and the shifting and line pressure control in the transmission, for example, will not be achieved. This of course is apt to undesirably increase shift shock produced by the transmission.